


The Mystery of the Multiverse

by perilpetrol



Category: Undertale (Video Game)
Genre: I just really like the idea of the multiverse, Multi, Multiverse Hopping, OC does end up with a sans, Other Additional Tags to Be Added, Psychiatrist OC, Readers are separate entities, Tell me if you think I should add some, Will be explained, but which one?, mostly in Underfell, some violence
Language: English
Status: In-Progress
Published: 2017-05-20
Updated: 2017-07-18
Packaged: 2018-11-03 01:37:57
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 2
Words: 4,074
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10956999
Author URL: https://archiveofourown.org/users/perilpetrol/pseuds/perilpetrol
Summary: Elisa Logan, a Psychiatrist and Research Psychologist, has been asked to work on a scientific research mission into the newly discovered Multiverse, but when she tries to leave after finding out how poorly staffed the mission, she is forced to complete it anyway. Now traveling through the Multiverse attempting to find a way back home, she encounters several groups of monsters, similar in appearance, but wholly different in personality. She also encounters a group of beings she calls "Inserts" As they seem to have been inserted into the worlds they reside with little to no physical traits, sometimes not even possessing discernable names. The baffling part is how little the others in the universes react to them.





	1. Scientific Exploration

**Author's Note:**

> Hi! This concept has been brewing in my head for a while, but I hope you enjoy reading it as much as I enjoyed writing it! And don't, I'm still continuing It Started on the Dance Floor if you have read that  
> Thank you for reading!   
> Tumblr: http://howdoihumanpls.tumblr.com/  
> NOTE* This work does not start in any Undertale Universe, but it will eventually take place in at least Undertale, Underfell, and Swaptale

1/18/210x   
Journal Entry 1  
Today I have been invited to join the scientific exploration colloquially referred to as Project RIMP or Research Into Multiverse Phenomen. This in itself is curious as I am not a scientist who you would first think of to be involved with a project such as this. I am a Psychiatrist and Research Psychologist, not a Physicist or any such field which would deal with matters of the physical. The one’s who invited me to partake in this expedition gave me the explanation that they did not know what types of people or creatures we would encounter, and a person who understands behaviors I would be the perfect person to negotiate with these people.   
I am unsure if I believe this logic, but, nevertheless, I will continue. If only to sake my continuing curiosity. This journal will serve to document the journey, and hopefully the people I meet along the way. I am scheduled to meet my fellow crew members tomorrow for the first time, I do not know if we will get along, but it’s not as if we have much of a choice in the matter. If I have an issue with my teammate I will simply deal with it, of course I will do so in the most petty way I can muster and still hold onto professional decorum. I am a scientist yes, but even someone like me will have their petty moments.   
I will not tolerate ignorance. 

 

1/19/210x  
Journal Entry 2  
I am not impressed by my fellow crewmates.  
Aside from me and one other, no one who is going on this expedition has a significant scientific background. And the one who does is a botanist, which, while handy to have as part of your team in theory, falls apart in practice when it is the only credential he has. The others are various military types, out of the four, three are Marines and one is Navy.   
I am losing confidence in this endeavor by the hour, much to the anger of my “team” they mistake my reasonable trepidation at participating in a scientific exploration with more than half the crew having no scientific credentials, for cowardice.  
They don’t understand, if we don’t have someone who understands exactly what’s going on we could get severely hurt, or worse. We could vaporized, we could be lost in the space between the multiverse, I don’t what will happen, and that is what worries me so much. Not enough thought seems to have been put into this mission. It looks as if those who set it up where only interested in the idea of a multiverse and didn’t properly think of a way to get there. I have been working on the project for a single day and I have already been berated by my fellow crew members and been forced to fix seven crucial mistakes in the planning. They thought I was being to cautious, I fired back that I would rather be cautious then dead. I am going to try to meet with the sponsors of this venture, if I don’t agree with the logic they present me as to the people they chose for this arguably important exploration, then I don’t care how many people call me a coward. I am leaving.   
1/31/210x  
Journal Entry 3  
It took me over a week to find the time to meet with my superiors, I was not impressed   
They told me I was acting overly emotional, that they had everything planned a certain way and to not worry my pretty little head over the details.   
I told them I was leaving.  
The response I got was chilling, they never stopped smiling, said I would change my mind and gave me twenty hours to do so, I am not taking it. I have already packed my bags and am leaving as soon as I return the key to the flat they had placed me in. I don’t care what scientific discoveries are happening here, we are grossly unprepared and uninformed. If I go through with this, there is a very likely chance I could die.  
I will not take that chan

***  
The sudden loud bang had me quickly looking up from my journal, frowning, the noise hadn’t sounded like a gunshot, nor did it sound far away enough to have been a bomb test. The sound had been close, and similar to that of a door being… slammed open. Oh, this wasn’t good, I pulled my computer over to me quickly, pulling up the cameras I had rigged in the doorway.  
It wasn’t what I had expected, someone breaking in to steal my things, it was two goons I frequently saw guarding the lab, though what they were doing trying to bust open my door was unclear. But before I could react, another loud bang was heard, as they managed to knock my door off it’s hinges, I scrambled up and ran to the window, barely making it before they broke through my bedroom door. I was on the first floor of a two story building, thankfully, so didn’t have to run down any stairs, nor did I have to fall any great heights. I did have to run however, and that was difficult as I am not the most athletic person, not overweight, just not strong. My heart was beating faster than it ever had, making me fear for it’s health, my lungs were burning with exertion and all my limbs felt colder. Maybe it shouldn’t have surprised me, then, when I felt someone large tackle me from behind and pin me to the ground, all the air was forced from my lungs. The man who had me pinned grabbed my hair and pulled my head up sharply, forcing me to face his companion, a hulking man with a wide set face, short brown hair and piercing blue eyes. His thin mouth was pulled up in a crooked grin   
“Thought you could outrun us Bitch? You look like you haven’t been forced to pick up a thing over ten pounds and you thought you could escape two trained security professionals? You must be even more stupid then I thought,” I fixed him with the strongest glare I could muster   
“I didn’t exactly have a whole lot of options, did I? At least this way you had to deal with the annoyance of hauling your fat-asses across-” I didn’t get to finish my sentence before I felt a hand crack across my face  
“What, no asking why we’re doing this too you? No snide comments about how many years we’ll serve in prison for this?” He growled, and spit blood on the ground before answering  
“Why expend the energy? I can’t exactly do anything at the moment,” In reality, I was almost certain this had been set up by the same people who had hired me in the first place. They had the whole area around the research facility monitored almost continuously, so there was no way they didn’t know what their own me were doing. I didn’t have strong theory as to why they were doing this though. The goon smirked at me  
“Finally, the first smart thing you’ve said,” I had more degrees than him, his parents, and his Grandparents had in total. “Now, we were told not to hurt you too much, but we can just say you got these trying to escape yeah?” I wanted to argue further, but the goon behind me slapped a strong smelling cloth over my mouth and nose, forcing me to inhale the fumes, the last thing I saw before slipping into unconsciousness was someone slipping a bag over my head. 

***  
The very first thing I perceived upon waking was the cold of metal around my wrists and ankles and stone underneath me. I opened my eyes to find I was in a dark cell, like I was a prisoner.  
No, I modified, I was a prisoner. The people who had employed me, whom I had trusted at least a minimum amount, had violently stolen me from my life for reasons I could not comprehend. Just how much was at stake with this mission that they would resort to kidnapping to accomplish it. And what was so special about me that they needed to force me to join their team when I refused to comply.  
I sat up against the wall, letting my eyes adjust to the dark, surveying the small space I had been afforded, it was a standard enough appearing cell, grey walls, a heavy door in one wall the only means of entry or escape. Either I was let out or I had to find a way through that door.   
After a while, the darkness turned more and more oppressive oppressive, filling my lungs, making it difficult to breathe, crushing me inside and out. My breaths sped up, slowly becoming hyperventilations, my skin was clammy, I was shaking, and my heartbeat was so fast it almost hurt. I felt as if I was dying, but I knew it was a panic attack. I hadn’t had one this bad in so long, I had always been able to coach myself down before it got like this. But at that moment, all I wanted to was let myself panic, because I had no idea what was going to happen, no idea if I was going to survive whatever was in store for me.  
I was so scared.  
Eventually, I was able to calm myself enough that I was no longer hyperventilating, and, when I could finally catch my breath. I began to cry, I was never one to let myself become an emotional wreck, only allowing myself short bouts of fierce frustration or anger outwardly. But I no longer cared, no one I respected would see me like this, and I wasn’t going to try to prove I was brave enough to not be scared, I wasn’t stupid enough to think they would show me any leniency. I fell asleep crying. 

 

***  
I awoke to find myself in a glass tube, one out of five positioned in a circle in the middle of a small room. The irony? I had been working in this very room a few days, it was the machine that would be used to transport us across the multiverse. Well, not the room itself, but the suits we would be rigged with, the suit I was currently rigged with, the room and the tube were so we didn’t get ourselves or anyone else who wasn’t part of the experiment hurt. Every other tank was filled, the other five members of my “crew” were passed out in them, each looking some degree of roughed up, like I had been.  
So I wasn’t the only one who fought this, interesting, as I was thinking this, a man in a crisp white lab coat walked into the room, the lead scientist who had apparently been in charge of setting everything up, a wide smile on his face  
“Good! So your awake! I’m sorry for the rough way we had to get you here, but we really needed to have this experiment run as smoothly as possible, and well… once you left the others started to question whether they should as well, heaven knows why, maybe they thought you were intelligent enough that your trepidation about the mission was some sort of sign.” He pulled some sort of small control panel out of his pocket and started fussing with it “You were certainly the only ones among your teammates that even conceptualized the idea that we were lying to you about the nature of the experiment.” He smirks up at me and I have the sudden powerful desire to throw a chair at him “Which we were, oh your still going to travel the multiverse, but no as scientists embarking on a grand exploration, but as common lab rats,” He pressed a few buttons before making his way to the door, turning to look at me at the last second.   
“Miss Logan? Try not to perish too soon,” Mere moments after he left the room, It felt like every single molecule in my body was being deformed, burning, squeezing pain that radiated and made it feel as though I was being deconstructed at the cellular level. Then, in a flash of light, we were gone.


	2. Underfell- A New Universe

**Summary for the Chapter:**

> It seems you have FALLEN.

**Notes for the Chapter:**

> I'm sorry for the long hiatus! I kinda got caught in a bad case of writer's block, but I hope you enjoy!   
> My Tumblr: http://howdoihumanpls.tumblr.com/

The crushing pain, the bright light, all persist for a solid minute before they abruptly shift. Suddenly, the pain is gone, and I find myself suddenly falling onto something cold and soft and wet. My eyes take a few moments to adjust to the far less bright light of whatever place we have been transported, and when they do I look around to find that we have been dumped in a strange cavern of sorts. Though there seem to be trees? And I appear to be lying on snow? My fellow “crewmates” groan and begin to awaken, four burly men and one skinny man  
“Rude awakening huh?” I ask, and they all swivel to face me, one man with blonde hair and blue eyes, I think his name was Robert, spoke first  
“Where the Hell are we? Why the Hell are you here? I thought you were leaving ‘because you thought this place was ‘Being grossly mismanaged’” He growls, as if I would be intimidated by his pathetic ramblings  
“I was leaving, on my way out in fact, when I was apprehended by two men who were employed by the same people we were. I woke mere moments before we were transported wherever the Fuck we are now and was informed we had never meant to be explorers, but only test subjects, to see if the technology was even viable,”   
“So you have no idea where we are either?” The Botanist, I think his name is Sam, a small man with brown hair and watery blue eyes. I shook my head, the two other men, one with red hair, and one with black and both with green eyes, Seth and Avery, scowled  
“What are we going to do then?” Seth, the redhead, asks, I shrug  
“Find out a way to work these suits and in the meantime hope to God that whoever lives in this Universe won’t react violently to our presence,” Just as I said this, a glowing red spear pierced the ground at our feet, just as a fierce scream pierced the air   
“NGAHHHHHHHHH!” We all simultaneously got up and started running in the opposite direction of whatever made that scream. It surprised me, as we ran, that it wasn’t me that was having the most difficulties, not Sam, but Robert. He was running significantly slower than the rest of an almost fell behind several times.  
“STOP RUNNING YOU COWARDS AND LET ME TAKE YOUR SOULS!” The voice said, too close for any kind of comfort, though the souls bit was confusing the message was plenty clear. There was no way I was going to stop running.  
Turns out, it didn’t matter if we were going to run or not, as a figure dropped down not twenty feet in front of us. It looked to be a fish woman, as crazy as that may sound, blue skin, fins and all, along with red hair, black armour and an eyepatch. I skidded to a stop, mere feet from her. She was grinning wide, every sharp tooth on display, I heard Sam whimper behind me, I think he peed himself  
“Get ready Humans, with your SOULS we will be freed from the Underground ONCE AND FOR ALL,” And with that, another glowing red spear appears in her hand, and she throws it right at me. I throw up my hands in a completely reactionary gesture, and, after a few seconds, look up to see why I didn’t feel any pain, and see both a red heart and shield hovering in the air before me, seemingly protecting me. The fish Lady grins even wider (which hadn’t seemed possible) and bellowed a laugh “If you want to survive Human, you have to face me head on! Let’s see what you got!”   
And then the battle truly started.   
***  
I am not only protecting myself with the shield, no that would be too easy! I figured out pretty quickly that only can the fish lady target the other members of my crew, she would without hesitation. I could expand the circle of rotation to safeguard the others, but it took significant concentration, which was not helped by both her increasingly teasing comments and my own team critiquing my every move. The spears were coming at me from every angle, and if I didn't look to see which ones were yellow, they would switch directions suddenly and I would be hit directly in what I learned quickly was my SOUL. Being hit directly in your SOUL, just in case you were wondering, hurts way too much. I couldn’t keep it up forever, unfortunately, and pretty soon, a spear hit Sam square in the abdomen, and unlike my soul, which absorbed most of the damage when it got hit, the spear went through him like a knife. I cried as he fell, blood gushing from the wound like...nothing I had seen before. My second of hesitation was all she needed apparently, as a moment later I felt a barbed, piercing pain in my chest, I looked down in surprise and saw the spear sticking out of my chest, blood pouring from the wound, staining the pristine snow beneath me a crisp crimson. I fell forward with a small sound of pain, nothing like the cry of my comrade, blood bubbling up my lips, choking my lungs.   
“HA! Now I have the SOULS I need to take to Agore!” I felt, numbly, The women who had killed me pick up my body and sling it over her shoulder “You’re the key to our freedom!” As she began to walk, I heard rather than perceived my last bloody breath pass my lips.   
This couldn’t happen. I was not going to die here, at the hands of a sadistic woman like that. I was not going to be slaughtered like this  
I was not a Lab Rat.  
I was too DETERMINED  
***  
I awoke in the same spot I had been when we were transported to this God-Awful Universe. My crew coming to around me, my head ringing like I was a bell recently struck. I was alive again, but I didn’t have enough time to wonder why, or how, I just picked myself and ran towards the trees  
“Logan!” Seth called out to me “What the Hell are you doing?!”  
“Don’t question it, just hide in the trees! And quickly!” I barked as I sprinted past him towards the dense forest, the others, clearly skeptical, do as I say, all the same, hiding among the trees. A few seconds later, we all heard heavy footsteps running up to where we just were, a coarse voice rang out  
“DAMNIT! I thought I saw something!” The growling voice made my breath catch and the center of my chest burn, I pressed a hand and felt a raised scar under the gray suit. It really had happened, I had died, and somehow I wasn’t dead now. The thought made me want to fall to the floor shaking, trying to process what that meant, but I didn’t have the luxury, not until I was out of this Universe, until I was safe at home, until this Monster was as far away from me as possible. A second, lighter set of footsteps was heard  
“CAPTAIN UNDYNE? DID YOU SEE THAT WHITE LIGHT COME FROM THIS DIRECTION AS WELL?” The new voice was loud, and decidedly male, though it had the same amount of haughty authority as Undyne’s, as that was apparently the woman's name,   
“You saw it too Papyrus? I thought maybe it was caused by a human, but I can’t find any!” A guttural growl rose up  
“CAPTAIN, WHAT WERE YOU PLANNING TO DO TO ANY HUMANS YOU FOUND?” Papyrus asked, with an air that said he already knew the answer  
“UGH, Papyrus! You’re not seriously listening to your brother are you?”   
“MY SISTER IN LAW IS A HUMAN, MY BEST FRIEND IS AN HUMAN, WE PROMISED THEM BOTH WE WOULD BRING NO HARM TO ANY HUMAN WE MET! WE CAN GET THE LAST SOUL SOME OTHER WAY, BUT WE WILL NOT BREAK OUR PROMISE,”   
“FINE! You wanna stay down here forever, BE MY GUEST,” The sound of stomping, retreating feet was heard, followed, a few seconds later, by a sigh, then, the voice spoke up again  
“YOU MAY COME OUT NOW HUMANS, CAPTAIN UNDYNE IS GONE,” I jumped, how had he noticed us here?! Acting with trepidation, I peeked my head around the corner and saw a tall, menacing, skeletal figure. He was dressed in black and red armour just as Undyne had been, and a large scar over one eye socket. His eye lights were focused on me, as he had obviously known exactly where I was. I yelped and ducked back behind the tree, heart beating rapidly.   
“HUMANS! DO NOT BE FRIGHTENED, I, THE GREAT AND TERRIBLE PAPYRUS WISH YOU NO HARM. I ONLY WISH TO BRING YOU BACK TO SCENIC MY HOUSE TO GET YOU TREATED FOR ANY INJURIES YOU MAY HAVE!” I closed my eyes and took a deep breath, attempting to calm myself, I had to look at this logically. While this Papyrus character was certainly intimidating, he hadn’t done or said anything to indicate he wanted to harm me or my crew, unlike Undyne. When I opened my eyes again, he was standing not two feet from me, I let out a small noise of surprise, flinching back against the tree. When Papyrus sees my fearful reaction, he pauses, and gets down on his knee so he is more at my eyes level, further demonstrating how much taller he is than me.   
“HU- Human,” He says, quieting his voice substantially when I recoil “Do not worry, as I reminded Undyne, there are some very important people in my life who share the distinction of being Human, I would not hurt you even if I wanted to. So please, let me help you,” He holds out a hand to me, I consider it for a fraction of a second before taking it, and he pulls me away from the tree  
“NOW,” He exclaims, volume once again at max “WERE YOU PERCHANCE TRAVELING WITH ANYONE ELSE?” I nod and call out   
“Guys! It’s ok to come out, he won’t hurt us!” My team slowly and suspiciously stepped out from behind the treeline. Sam, upon seeing the skeleton, made a squeaking noise and ducked behind Avery, who was wearing a similar expression of shock of fear, same with Seth. Robert looked like he was about to piss himself in fear  
“W-what the hell are you? Who are you? Where are we?” Robert asked Papyrus pulled himself up to his full, impressive, height   
“I, THE GREAT AND TERRIBLE PAPYRUS, AM I MONSTER! THE SAME AS ALL THE CREATURES OF THE UNDERWORLD, WHERE YOU HAVE HAD THE MISFORTUNE OF FALLING!”   
“Why did that Undyne lady want to kill us?” I asked softly, my brow furrowed, Papyrus looked almost uncomfortable at the question  
“WELL, YOU SEE … MONSTERS WERE TRAPPED UNDERGROUND A LONG TIME AGO, AND THE ONLY WAY TO ESCAPE IS TO USE SEVEN HUMAN SOULS, I USED TO THINK HUMANS WERE EVIL JUST LIKE EVERYONE ELSE, BUT ONCE I MET Y/N AND FRISK I HAVE REALIZED HUMANS ARE JUST LIKE MONSTERS! WELL, ASIDE FROM THE OBVIOUS,” I winced as he talked, a sharp static noise was all I heard instead of what was obviously supposed to be a name  
“Who?” Seth asked, frowning,  
“Y/N, AND FRISK OF COURSE! DID YOU NOT HEAR ME? ARE YOUR EARS THAT PITIFUL?” Seth stepped forward, a sneer on his face, but I put a hand on his shoulder and stopped him   
“Forgive me, but I don’t think it’s a good idea to have this conversation out in the open, you did say that a human soul is needed to break the barrier, that seems like something everyone would want,” Papyrus nodded  
“COME ALONG, HUMANS! WE SHALL ALL VISIT SCENIC MY HOUSE!”

**Author's Note:**

> NEXT!  
> Underfell- A New Universe


End file.
